The textile industry has long used a variety of mechanical and chemical operations to give fabrics and garments their ultimate feel and performance characteristics. Recently, the textile industry has seen tremendous growth in the development of new finishes for garments, such as Prewash, Soft Hand, Stonewash, Bleach, Acid Wash, Garment Dye, and combinations thereof. With growth of new finishes for garments, the textile industry has also seen the reintroduction or resurgence of garments with durable press, shrink-proof, water-repellent, fire-retardant and soil release agents, and other specialty finishes.
For illustration purposes, the background will focus on the techniques and problems with applying durable press finishes to garments. A durable press finish allows a fabric or garment to be washed and dried by conventional methods and still recover or retain an ironed appearance without pressing. The same or similar techniques used in applying durable press finishes are also used in applying other finishes. Therefore, the background's focus on durable press finishes is not intended to limit the presently disclosed invention in any manner.
For many years, the textile industry has had applied durable press finishes to cotton and cotton blended fabrics. This finishing is done by the application and curing of one or more resins including melamine formaldehyde, urea formaldehyde, polycarboxylic acids, and dimethyloldihydroxyethylene urea. A finishing technique using formaldehyde is disclosed in U.S. Pat. No. 3,275,402 which relates to imparting crease recovery properties to cellulose fabrics by impregnating the fabrics (in the presence of water) with formaldehyde, a water-soluble metal salt, and a polymeric film forming stiffening material capable of reacting with formaldehyde, and curing the impregnated material to cross-link the cellulose and bond the film forming material to the cellulose.
The two standard techniques for applying durable press finishes to fabrics are the pre-cured technique and the post-cured technique. The pre-cured technique involves applying a pre-cured resin finish by padding on the finish, framing to width and drying on a finish frame (pin or clip), and curing in an oven. The post-cured technique is the same as the pre-cured technique except the curing step is omitted to prevent the finishing resin from cross-linking with the cotton. After a garment is made from post-cured fabric, it can be pressed and then cured in the pressed configuration so that creases, pleats, seams, belt loops, etc., maintain their "new" look and the panels of the garment remain smooth even after repeated laundering.
Whether using the pre-cured or post-cured technique on garments, the finishing resins are currently applied through the use of industrial washers. However, one of the primary problems with applying the finish is that durable press resins lack affinity for cotton. Thus, these durable press resins do not exhaust to the fabric as may certain dyes and chemicals. Therefore, using an industrial washing machine to apply resins is inefficient because it is necessary to run a liquor ratio (weight of liquid to weight of garments) of at least 4:1 in order to achieve uniform saturation. Assuming that the garments will be extracted to between about 50 to 100% percent total add on, four to eight times more resin has to be in the bath than is accepted by the garment. For example, if 5.0% resin is needed to achieve a desired finish, 40.0% resin would have to be added to a washer (assuming a 4:1 liquor ratio and extracting to 50.0% total add on). Since such large amounts of resins are necessary, it would be advantageous to recover the resin which is not accepted by the garment. However, it has been found that reclaiming the resin leads to contamination. Thus, most resins are wasted rather than recovered which makes this technique of applying finishing resin very costly.
In an attempt to overcome the inefficiency of using a washer for applying finishes to garments, other methods have been devised including the "Dip & Drip" method and the use of manufactured foam.
The "Dip & Drip" method is a slight improvement over the washer method. In this method, garments are collected in a water permeable bag, dipped in a resin finish mix, allowed to drip the excess finish back into the mix tank applicator, and then extracted. While the amount of unused finish mix has been greatly reduced, it is still a significant problem.
The method of using manufactured foam entails entraining the resin within a foam. Although manufactured foams are generally applied to piece goods by continuously metering a predetermined amount of foam on to the surface of the piece good, manufactured foams can also be applied using the washer method. Using a manufactured foam to apply finishes to garments does reduce waste, however the use of manufactured foam requires strict control of many process parameters and the purchase of expensive foaming equipment. A further disadvantage is that the finish may be distributed in a random and uneven fashion. Although this random and uneven distribution may be advantageous when it is desirable to create a blotchy effect on the fabric, such as when applying a dye to achieve a certain pattern, it is a disadvantage when applying finishing, such as durable press, shrink-proof, water-repellent, fire-retardant and soil release agents, and other specialty finishes, where coating the fabric evenly and smoothly is essential.
To truly become efficient, garment producers need a way to apply finishes to garments with no special equipment that distributes the finish evenly and smoothly with minimal or no wasted resin.